Telegraph system employing link circuits



March 27, 1934. E. M. s. McWHIRTER ET AL 1,952,601

TELEGRAPH SYSTEM EMPLOYING LINK CIRCUITS Original Filed Oct. 25, 1930 9 jack 5: 5 MS. MWH/RTER WVENTORS J. a. FLINT A TTORNEV Patented Mar. 27, 1934 UNITED STATES TELEGRAPH SYSTEM EMPLOYING LINK CIRCUITS Eric M. S. McWhirter and James G. Flint,

Aldwych, London,

England, assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Original application October 25, 1930, Serial No. 491,114. Divided and this application February 6, 1932, Serial No. 591,286. In Great Britain November 6, 1929 11 Claims.

This invention relates to an exchange system for the interconnection of subscriber telegraph apparatus.

The subject matter herein claimed is divided from applicants application, Serial No. 491,114,

filed October 25, 1930.

In systems embodying the invention, the signals for setting up the connection and the telegraph message impulses after the connection has been set up are sent from a substation over the same circuit and consequently an object of the invention is to improve such systems.

A feature of the invention comprises the means whereby each substation is connected to the exchange by two wires only which form a complete metallic circuit for the signals for setting up the connection and for telegraphic communication to and from the substation.

Another feature of the invention relates to the means whereby the operators at the. exchange are provided with printing telegraph apparatus and each cord circuit contains means for connecting thereto this apparatus so that any com- I munications between subscriber and operator are carried out solely by means of type printing telegraph apparatus.

A feature of the invention is a novel junction circuit which comprises two junction lines only and relays at each end of the junction line connected to repeat telegraph signals in the respective directions and so arranged as to remain unaffected by messages in the opposite direction.

Circuits embodying the invention will now be described in connection with the accompanying drawing in which:

Fig. 1 represents the apparatus at a subscribers station and the apparatus associated with his line at the exchange;

Fig. 2 shows an operators cord circuit;

Fig. 3 shows a junction circuit for the interconnection of two telegraphic exchanges; and

Fig. 4 shows a cord circuit'by means of which any subscriber may be connected to a plurality of other subscribers.

A teletype apparatus located ata subscribers station comprises transmitter contacts TC, which when operated by a keyboard or automatic transmitter will open and close a line circuit in accordance with the signals which are to be sent. These contacts are normally closed. The apparatus also comprises printing mechanism'controlled by a relay PM responding to the received impulses and a motor TM which drives the mechanism both for printing-and transmitting pur poses. A relay RM of the slow-release type is connected in series with the transmitter contacts and relay PM. The motor is adapted to be connected to the lines P1, P2 of a local source of electric lighting or power supply over the normally open contacts of the relay RM. Contacts TMC are arranged to be closed whenever the motor is running. The subscribers lines L1, L2, leading to the exchange are closed at the substation through the slow-release relay RM, receiving relay PM, the normally closed transmitter contacts TC, a condenser K, and a pair of polarized relays PR1 and PR2. The polarized relays are arranged to operate simultaneously on a battery reversal through the condenser K and will remain in the position to which they were last operated.

In order to initiate a call, the subscriber momentarily depresses a non-locking key CK which closes the circuit of the motor TM which immediately closes its contacts TMC. A calling relay CR at the exchange and the relay RM thereupon operate in a circuit from the positive pole of battery U, contacts of jack CJ, line L1, relay RM, relay PM, contacts TC, normally closed contacts of relay PR1, key RK, contacts TMC, line 12, contacts of jack AJ, relay CR, contacts of jack CJ, negative pole of battery. Relay CR operates, lights a calling lamp CL and a pilot lamp PL and rings an alarm bell AB.

The operator inserts her answering plug AP into the jack AJ and throws the key CCK to the left. This connects her type printing telegraph apparatus OM in series with that at the subscribers station and with the battery U, the circuit being as follows: positive pole of battery U, contacts of jack CJ, line L1, relay RM, relay PM, contacts TC, contacts of relay PR1, key RK, contacts TMC, line 12, ring spring of jack AJ, ring of plug AP, contacts of key CCK, operators machine OM, back contact of relay CSR, contacts of key CCK, tip of plug AP, tip spring of jack AJ, and negative terminal of battery U. The operator then by typing asks the subscriber for the wanted number which is thereupon typed back to her.

Local call Assume first that the wanted subscriber is on the same exchange. The operator inserts a plug CP of the cord circuit into the jack CJ belonging to the wanted subscriber. The sleeve of the jack CJ is grounded which serves a purpose to be mentioned later and also operates the relay CSR. The battery connected to the springs of the jack CJ Of the called subscriber is disconnected and all battery supply is then derived from the battery U of the calling subscriber. The condenser E. of the called subscriber is charged by the battery U of the calling subscriber, the connection being as follows: positive battery U connected to the line L1 of the callin subscribers set, line L2, ring of jack AJ and of plug AP, key CCK, contacts of relay CSR, ring of plug CP and of called subscribers jack CJ, line L2, through the called subscribers set which includes condenser K, line L1 tip of jack CJ and of plug CP, contacts of relay CSR, tip of plug AP and of calling subscribers jack AJ, and negative battery U. The operator then throws the key CCK to the right and thereby reverses the connections between the tips and rings of the plugs AP and CE. The key CCK in this position connects the tip of plug AP to the ring of plug CP, and the ring of plug AP to the tip of plug CP. A charging current of short duration flows from battery U of the calling subscriber to condenser K of the called subscriber, the charge on the condenser K being opposite in polarity to that impressed upon the condenser in the circuit previously traced just before the key CCK. was thrown to the right. The charging current is sufficient to operate the relays PR1 and PR2 of the called subscribers set. Relay PR2 closes the circuit of the subscribers motor which commences to rotate. The operator then restores the key CCK to normal and relays PR1 and PR2 restore. The relay RM operates and closes its contacts, thus keeping the motor running.

The connection between calling and called subscribers is thus complete and communication may take place. A message may be sent by the calling subscriber and received on the called subscrlbers instrument in the absence of any operator at the substation.

The operator at the exchange may connect her own machine OM in series in the circuit by moving the key CCK to the left, the circuit then being positive pole of battery U, contacts of jack CJ, line L1, calling subscribers apparatus, line L2, ring spring of jack AJ, ring of plug AP, contacts of key CCK, operators machine OM, contacts of key CCK, operated contacts of relay CSR, ring of plug CP, called subscribers apparatus, tip of plug CP, contacts of key CCK, operated contacts of CSR, (two sets), contacts of key CCK, tip of plug AP, tip spring of jack AJ, contacts of jack CJ, negative battery. Thus the operator is able to satisfy herself that a satisfactory connection has been completed.

When the key CCK is restored to normal, relay SR is included in the line circuit between the two subscribers. This relay is made slow to release so that the normal telegraph impulses do not cause it to de-energize.

The release of the connection is under control of the calling subscriber and in order to release he presses the key RK. This key breaks the short circuit which had been maintained around the relays PR1 and PR2 and condenser K and causes the relays RM at each station to de-energize. This key RE is held down until the contacts of relay RM open after a predetermined time and so stop the motor whereby the contacts TMC open.

Q It may then be assumed that the motor at the called station has also stopped. The opening of the line circuit causes the de-energization of the relay SR at the exchange and this closes the circuit of the thermostat relay THR, which oper- J ates after a delay which is sufficient to ensure that the motors at the calling and called stations have stopped and the supervisory lamp SL is lighted. This signals to the operator that the lugs may be removed from the jacks.

Trunk or toll call If the calling subscriber should require a connection to a subscriber on another exchange the operator inserts the plug CP into the jack OJ belonging to the junction circuit shown in Fig. 3. Two telegraph relays are provided at each end of a junction circuit. Relays A and C have each two windings denoted by Al and A2 and C1 and C2, respectively. lhese relays are polarized and their armatures are biased toward the spacing contacts. The relays B and D are telegraph receiving relays. Normally, when the junction circuit is idle, relay A is operated in a circuit extending from the negative terminal of the local battery G over the operating winding A1, back contact of relay B, back contact of relay M, back contacts of relay R, another back contact of relay Il/I, resistance and positive battery G. Relay C operated in a similar circuit from battery H. The junction lines JLl and JL2 are normally connected in series over the windings of B and D, the holding windings A2 and C2 and marking contacts of relays A and C.

When the operator inserts the calling plug CP into the jack OJ, relay M operates to ground over the spring of the jack OJ and disconnects the above circuit for winding A1, but at its upper front contact relay M switches the battery U (Fig. 1) through to relay A to maintain the winding A1 of the latter in a circuit from negative battery U (Fig. 1), upper spring of jack CJ, tip of jack AJ, tip of plug AP, uppermost left made contact of key CCK, resistance, front contact of relay CSR, uppermost right contact of key CCK, tip of plug CP, tip of jack OJ, upper front contact of relay M, winding Al, back contact of relay B, ring of jack OJ, ring of plug CP, inner right made contact of key CCK, front contact of relay CSR, inner left made contact of key CCK, ring of plug AP, ring of jack AJ, line L2 to line L1, rin of jack CJ to positive battery U.

Upon the key CCK (Fig. 2) being thrown to the right the current in the winding A1 is reversed and causes the armature of relay A to move over to its spacing contact. The armature in this position closes the circuit through the operating winding of relay D at the other end of the junction line in series with the holding winding C2 of relay C and battery S at the outgoing end of the junction line. The complete circuit is from the negative terminal of battery 8, armatures of relays E and A, junction line JLl, armature of relay C, winding C1 of relay C, winding of relay D and line JLl. The current in the holding winding C2 of relay C ai s that in the operating winding and keeps the armature on its marking contact when the relay D is operated. During the time of movement of the armature of relay D, the winding C1 is disconnected but a current in the winding C2 prevents any operation of the associated armature. Relay F is then energized in series with the winding C1 and operates a relay CR to light the calling lamp. The operator at the second exchange inserts her plug AP into the jack IJ at the other end of the junction circult and this causes the operation of relays Q and N to local contacts on the jack, Q being slightly slower to operate than N. Relay N disconnects the Winding C1 from the local circuit and reconnects it in the following circuit: tip spring of jack IJ on the right of the figure, lower contact of relay Q, battery EB, upper contact of relay Q make contact of relay N, winding Cl, break contact of relay D, back to the ring spring of the jack L]. This circuit: is at the moment open at the relay D, but as soon as the operator at the first exchange restores the key CCK to normal, relay A operates to its marking contact and the windings C2 and D are de-energized. The armature of relay D is released. During the movement of relay D there is a short time when both windings C1 and C2 are de-energized, but relay F is made slightly slow to release so that any movement of relay 0 will be without effect at the left-hand end of the junction circuit. As soon as relay D has released, the winding Cl is energized in the circuit previously traced. When relay N operates, the circuits for relays F and CR are broken and thecalling lamp extinguished. The operator at the second exchange can now type to the operator at the first exchange, transmission from the second to the first exchange being relayed by relays C and B and transmission from the first exchange to the second exchange being relayed by relays A and D. The calling subscriber is in series in the circuit with the machine of the operator at the first exchange and so can follow the progress of the call.

The operator at the second exchange upon ascertaining the requirements of the call inserts her plug CP into the jack of the wanted subscriber. The connections and operation are similar to a local call on this exchange except that the telegraph relays C and D take the place of the calling subscribers machine in the circuit and the necessary signaling current is supplied by the battery EB instead of by the battery U in Fig. 1. When the keys CCK of both operators cord circuits are restored to normal the two subscribers are in communication, but either operator can monitor on the circuit so long as her key CCK is kept to the left.

The release of the connection takes place in a manner similar to that on a local call, the relays TI-IR in each cord circuit operating to light their respective supervisory lamps.

If a subscriber wishes to send a message simultaneously to a plurality of other subscribers, the apparatus shown in Fig. 4 is utilized. The subscriber originates the call in the normal manner and the operator plugs into jack AJ (Fig. 1) with a plug AP (Fig. 2) in the usual way. When the requirements of a subscriber have been ascertained, the operator inserts the plug CP into the jack BJI in Fig. 4 which connects the tip and ring of the plug GP to a telegraph relay TR. The tongue and marking contacts of this relay are connected through a battery and resistance to the tip and ring springs of a second jack BJ2 into which the operator can insert a plug APB. The plugs CPl to CP4 are inserted into the calling jacks of the required subscribers or into the jacks of junction circuits if the subscribers are on another exchange. Sleeve relays SRl to SR4 complete the circuits to these plugs only when they have been inserted into a jack. Pressure of the key BCK reverses the connections to all the subscribers lines and thus starts the motors at all the called stations into operation. The calling subscriber can then transmit to all the called subscribers circuits in parallel.

In many cases it will be necessary in order to ensure satisfactory transmission that the batteries U, EB, etc., providing the signaling cur- ,rent should be of a voltage considerably in excess of that used for telephone exchange working and it will be observed that in all cases the sleeves of the jacks, contacts of which are connected to these signaling batteries are grounded, so that the sleeve of the plug is also grounded and the operator effectively protected against shocks.

What is claimed is:

1. In a signaling system, a telegraph set, a junction circuit comprising a transmitting and a receiving relay, a line circuit normally including a winding of the receiving relay and extending to a distant station, means for connecting the telegraph set with the transmitting relay and means responsive to such connection for disconnecting the receiving relay winding from the line circuit and replacing it by the transmitting relay contacts and a source of current in series therewith.

2. In a signaling system, a telegraph set, a junction circuit terminating in jacks at the ends thereof and extending between operators positions, said circuit at one terminal including a transmitting and a receiving relay, a line circuit normally including a winding of the receiving relay and extending to the operators portion at a remote end, means for connecting the telegraph set with the transmitting relay and means responsive to such connection for disconnecting the receiving relay winding from the line circuit and replacing it by the transmitting relay contacts and a source of current in series therewith.

3. In a telegraph system, a pair of terminal telegraph sets, a junction circuit adapted to be connected to each set, a line connecting the junction circuits with each other, each junction circuit comprising a transmitting relay, a receiving relay and a battery, means for connecting said relays with the terminal set, and contacts on the transmitting relay adapted to connect the battery across the line when in de-energized position, and the receiving relay across the line when the transmitting relay is energized whereby the receiving relay in one junction circuit is energized upon the de-energization of the transmitting relay of the other junction circuit.

4. A telegraph system as defined in claim 3, which further comprises a source of current controlled by the terminal set for energizing the transmitting relay of the associated junction circuit.

5. A telegraph system as defined in claim 3, comprising also means for maintaining the transmitting relay energized when the junction circuit and the associated terminal set are disconnected.

6. In a telegraph exchange orfice, a line extending to a transmitting subscriber, a two-wire line extending to each of a plurality of receiving subscribers, and a conference circuit whereby messages sent by the transmitting subscriber may be received simultaneously by all of the receiving subscribers, said conference circuit comprising a receiving relay in the transmitting subscribers line, a pair of terminals connected to each other through a source of current and contacts of said relay, and manually operable means for connecting the line of any one or more selected receiving subscriber across said pair of terminals.

'7. A cord circuit for setting up broadcasting connections in a telegraph exchange ofiice cornprising a plug suitable for operative connection to a line from which signal impulses are to be broadcast, said plug having connections in parallel to a plurality of relay contacts, and other plugs having three terminals, one of which upon association with the jack of a line closes contacts to its other terminals through a relay individual to the plug thereby connecting terminals of said second named plug directly to terminals of said first named plug.

8. A junction circuit for telegraph systems including a telegraph impulse repeating means comprising relays, each end of said circuit being provided with two jacks, a cord circuit for connection with said jacks, means connected to one jack at each end of said circuit whereby upon application of said cord circuit thereto battery is supplied over said cord circuit to operate a relay or" said repeating means, and means connected to another jack at each end of said circuit Whereby upon application of said cord circuit thereto battery is supplied to said cord circuit over a relay contact of said repeating means.

9. A telegraph system comprising a transmission line terminating at a pair of jacks, said jacks having two of their respective terminals in multiple, two other of their respective terminals normally in multiple, and two other of their respective terminals connected by a path including a source of potential.

10. A system in accordance with claim 9, in Which one jack is provided with auxiliary contacts operable by application of a plug thereto to close the operating circuit of a relay.

11. A system in accordance with claim 9, in which one jack is provided with auxiliary contacts operable by the insertion of a plug therein to close the operating circuit of a relay and the other jack is provided with auxiliary contacts operable by the insertion of a plug therein to close the operating circuit of another relay.

ERIC M. S. MCWHIRTER. JAMES G. FLINT. 

